1. Field
This disclosure is concerned with a nutritionally balanced food composition and specifically with a ready-to-use liquid elemental diet which is non-browning at elevated temperatures.
2. Prior Art
Nutritionally balanced diet compositions have been known and available for many years. Typically, such compositions include carbohydrate, protein and lipid components as well as vitamins and minerals. In the case of so-called elemental diet compositions, the protein component may be made available in a nutritionally desirable balance of low molecular weight peptides and/or amino acids. Unfortunately, when amino acids and carbohydrates are combined in an aqueous solution, these components have a tendency, especially with time and at elevated temperatures, to result in a brownish solution and form undesirable by-products due to the well known Maillard reaction(s).
It is well known that this generally undesirable color change (which includes the formation of somewhat toxic melanoidin end products) is associated principally with the pH of the carbohydrate-amino acid solution. The pH controls the chemical state of the reducing end groups of available carbohydrates and the amine groups of the amino acids or peptides. Inhibition of Maillard browning reactions may be accomplished by (1) maintaining the solution pH below the isoelectric points of the amino acids and peptides (e.g. less than about 4.2); (2) keeping the solution temperature as low as possible during processing and storage; and/or (3) by increasing the mean distance between reactants (e.g. a 3.1% solution of amino acids is less likely than a 6.2% solution to form solution browning reaction products with glucose.
In general it has been known that the undesirable products and coloring of the Maillard reactions can be avoided or minimized by maintaining the pH below about 4.5. See, for example, U.S. Pat. No. 4,144,357 which summarizes some of the earlier observations in this area. See also the disclosures in U.s. Pat. No. 2,426,639 showing various ways to assure a low pH while still keeping a food product palatable.
Even though it has been known that the Maillard reaction(s) could be avoided or minimized by maintaining a relatively low pH, it has been difficult for elemental diet manufacturers to provide such diets in a ready-to-use, liquid form because of the known lack of stability of lipid emulsions in the pH range needed to avoid the Maillard reactions. Because of this, until very recently (e.g. the recently announced CRITICARE ready-to-use liquid elemental diet, Mead-Johnson Corp.), manufacturers have provided liquid elemental diets in a dry form, typically in a foil packet which must be mixed with water just prior to use. Aside from the obvious inconvenience of having to mix a dry powder prior to use, it can be appreciated that the very act of mixing raises possibilities of contamination which can be of concern vis-a-vis the environment (i.e. hospital patients) in which liquid elemental diets are often used.
Quite surprisingly, it has been found that stable, heat-sterilizable elemental diet compositions can now be prepared in a liquid form. The product, being ready-to-use, avoids the disadvantages associated with elemental diets in dry form. Details of the discovery are described below.